Human skin is made up of three layers. The outer layer is called the epidermis. "Epidermis" is from the Greek words "epi" meaning "on" and "derma" meaning "skin". It is a tough protective layer that contains melanin. Melanin both protects skin from the sun and gives skin its pigmentation.

Under the epidermis is the second layer called the dermis. It contains nerve endings, sweat glands, oil glands, and hair follicles.

Beneath the dermis is the third layer composed of subcutaneous fat. "Subcutaneous" means "under the skin".

Human skin is quite different in thickness in different areas of the body. The skin on the palms, fingers, soles, and toes is somewhat thicker than in other places. Skin colour becomes white from the opaqueness produced by the increased water content of the skin. Skin that has been submerged under water, such as your hands when washing dishes, appears wrinkled and shriveled up too.

Most people believe that this appearance is due to the skin shrinking. Quite the opposite is the case. The skin is actually expanding from the absorption of water.

Water is absorbed by skin immersed in water through the process of osmosis. This is because the internal body fluids of humans are more concentrated than in fresh water. Skin whitening, wrinkling and shriveling up appear because these areas of thicker skin expand as they become saturated.

Skin elsewhere on the body soaks up water after prolonged immersion. However, because this skin is thinner, there is more room for moisture, and the whitening, wrinkling, and shriveling up takes longer to appear.

Interestingly, the whitening, wrinkling, and shriveling do not occur from ocean salt water. This is because sea water is very similar to the fluids in the human body and osmosis does not take place.

Interesting facts

The skin of the average adult has a surface area of between 1.5 and 2.0 square meters. Most of this is between 2mm and 3mm thick.